The present invention relates to a multi-ink-jet head in which the density of an array of ink distribution tubes each having a nozzle at one end thereof can be increased and the width of a nozzle array may be made desirably selected.
In the prior art multi-ink-jet heads, a plurality of ink distribution tubes or passages are branched from an ink manifold, extended in a row and communicated with nozzles which emit continuous streams of ink and one piezoelectric element is mounted on each ink distribution tube. An electrical signal is applied selectively to the piezoelectric elements so that the ink in the excited ink distribution tubes is pressurized and emitted through the nozzles.
The piezoelectric elements cannot be reduced in size beyond certain limits because of their mechanical characteristics or properties and due to some technical problems encountered in the fabrication of the elements. As a result, the nozzles of the ink distribution tubes are arrayed at a predetermined pitch, but the root portions of the ink distribution tubes which are closer to the ink manifold and on which are mounted the piezoelectric elements must be arrayed at a pitch larger than the nozzle pitch so that the contact with the adjacent piezoelectric element can be avoided. Therefore, the ink distribution tube array has a front width (that is, the width of the nozzle array) shorter than a root width along the ink manifold, so that it is in the form of a fan with the ink distribution tubes converging slightly toward the front end of the tube array. In consequence, the direction in which the stream of ink is emitted is different from one nozzle to another. Thus, in the prior art multi-ink-jet heads, a number of ink distribution tubes or passages has been limited, so that a number of nozzles is limited and subsequently the width of an array of streams of ink-jet is limited and narrow.